A study of magnetodielectric effects in the ferroelectric antiferromagnetic system

The anomalies in both the dielectric constant and loss tangent occur at fixed temperature close to the magnetic ordering transition, which had been observed experimentally in multiferroic pervoskite YMnO3 and BiMnO3, indicating coupling between the magnetism and dielectric properties. In this paper, we apply the Heisenberg model for magnetic interaction and single-well potential model for electrical interaction to analyze the magnetodielectric effects in the system with the spontaneous coexistence of ferroelectric and antiferromagnetic orders below a certain temperature. By adding an appropriate coupling term between the magnetic and electrical subsystems as g ∑ k , 〈 i , j 〉 q k 2 s → i · s → j , we find that a rather smooth magnetic field dependence of dielectric constant ε occurs near the antiferromagnetic transition TN, and application of magnetic field induces a fairly large enhancement of ε around TN, which is consistent qualitatively with experimental and phenomenological theory results.